Hypertrophic cardiomyopathy is the most important inherited heart disease. It is characterized by markedly thickened walls of the left ventricle (LV) of the heart. In about 25% of the patients this results in obstruction to the flow of blood out of the LV. This is often associated with severe symptoms such as chest pain, shortness of breath, palpitations, dizziness, blackouts, and fatigue. Traditionally, patients with obstructive hypertrophic cardiomyopathy who have failed to benefit from drug therapy have been offered cardiac surgery to relieve the outflow tract obstruction. However, this is a major undertaking and is associated with about 5% operative mortality and significant morbidity. Dual chamber pacing, by altering the contraction pattern of the LV has the potential to open up the LV outflow tract. In this study 44 consecutive patients with obstructive hypertrophic cardiomyopathy and with severe symptoms who had failed drug therapy were treated with dual chamber permanent pacemaker. This resulted in marked alleviation of symptoms in most patients associated with a reduction in the LV outflow obstruction. Importantly, the favorable effects of long term dual chamber pacing persisted when pacing was acutely discontinued suggesting that chronic pacing results in secondary changes at a cellular/molecular level.